How to fix System Data taking up 150GB?

You can’t directly manage the contents of system data. That is done by macOS. The category varies in size depending on the current state of your Mac.

What you can do to create more free space:

• Reboot your Mac at least weekly. Let the OS do housekeeping and clear caches.

• Empty the Trash in the Dock. 

• Empty the trash in the Photos app.

• Delete unused and unneeded application installers from your downloads folder and desktop. No need to store on your Mac what you can freely download any time.

• Transfer files that you don’t use daily to an external drive and then delete them from the startup drive and empty the trash. Files that take up the most room are movies, images and music.

This from Apple on the subject of freeing up space:

Free up storage space on Mac - Apple Support

Also, please see this guidance from Apple: 

Find and delete files on your Mac - Apple Support

Also: How to Use Finder to Clear “System Data" on a Mac  (Thank you, TheLittles!)

Just to add to the good suggestion by my colleague

Reducing System/Volume/Data is a common question. 

1. Quick Fix Actions:

   For Apple Silicon computers, use Disk Utility to erase a Mac.

   For Apple Intel computers, use Disk Utility to erase an Intel-based Mac, then reinstall macOS.

   Always make a Time Machine backup before proceeding.

   Migrate only the user account, not the entire system.

   Reinstall only the necessary applications from the Apple App Store or directly from the developers.

2. Detailed methods that may or may not work 

A -  System data taking too much in MacOS Sono… - Apple Community

B - Time Machine Local Snapshot won't delete - Apple Community

C - Over 60% storage blocked by System Data - Apple Community

D - Running out of storage - system data is huge after upgrade to macOS Tahoe 26.2

How to free up ‘System Data’ and other storage on your Mac from a fellow colleague  @ neuroanatomist

Use another application to see where space is being used  Storeograph  Directly from the Developer 

View APFS snapshots in Disk Utility on Mac

➡️ Suggest getting an External SSD Drive and start moving your Pictures, Videos, Music and any other large files you have control over, OFF the Internal drive and Onto the External ⬅️

Understanding iCloud Drive from a well written User Tip from @ Richard.Taylor

3.- Generally

When the user discovers this issue, it’s likely because the computer’s internal drive capacity is small, such as 256 GB

The user’s storage needs may have increased since the computer was purchased. To future-proof the computer, consider spending extra money upfront on a larger drive capacity and adding more unified RAM.

Note - On Apple Silicon and newer computers. The SSD Drive and the Unified RAM are Soldered to the Logicboard and can not be upgraded.

System Data used to be called the Other Category in previous systems. The Other category is a potpourri of files which can include:

• System temporary files

• macOS system folders

• Archives and disk images (.zip, .iso, etc. - often found in the Downloads folder)

• Personal user data

• Files from the user’s library (Application Support, iCloud files, screensavers, etc.)

• Cache files: browser, Mail

• Mail messages & attachments

• Fonts, plugins, extensions

• Safari reading list

• iTunes backups

• Crud resulting from jailbreaking your iDevice

• Game data

• Saved data files

• Call history

• Notes

• Media

• Voice memos

• Other files that are not recognized by a Spotlight search

• Media files that cannot be classified by Spotlight as a media file because they are located inside of a package

• Files created and modified by other user accounts on your Mac.

They can be located anywhere on your hard drive.

The files that you have control over are located in the Documents, Downloads, Pictures, Music and Movies folders.  You can use either of these two free apps, GrandPerspective  or OmniDiscSweeper, to find the largest files on your drive so you can determine if they can be deleted or moved to an external HD for storage.  I prefer GrandPerscective from a GUI point of view but try them both and see which works best with you.

Note: you can empty the Downloads folder after the apps and/or updates that were downloaded have been installed or applied.  Many users have found a couple of Gigabytes of files in their Downloads folder which are no longer needed. 

I have stated this before but if after trying all and no change then you need to boot into recovery, erase the reinstall the OS and then migrate all back. Just did one today for a friend and it reduced the system data quite a bit. I have done this on my own Macs and it works.

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